Stator Removal / Replacement Write Up

Well after getting home and having a good nights sleep it was time to have a look at the bike and find out why the battery wasn't charging.If you are new to bike electrics this could seem like a daunting task but in reality there are only a few components in the charging system and one of them can't possibly go wrong.The whole system consists of (from engine up) a set of rotating magnets, a stator (a set of static coils), 3 wires, a connector, reg/rec, another connector, 2 wires, main fuse and battery.Fault finding is relatively easy too, I was going to type it out but there is already a fault finding flow chart that can be seen here or if that link is broken it can be downloaded from here free.The stator readings for the 900 should be 1.8 - 2.8 ohms

Right now to the job itself.I guess you should disconnect the battery for safety reasons but I didn't and couldn't see how this would be a problem (sparx correct me if I'm wrong on H&S grounds).Always remember folks make a note of which bolts go where.

Start by taking the gear lever off by undoing the Allen bolt

then remove the plastic cover.

Speedo pick up cover to reveal the pick up sensor and rotor. And the gear lever linkage noting it's alignment on the shaft.

Remove the rotor (14mm nut), note the washer behind it.

And the sprocket cover.

Now go to the reg/rec and unplug and feed the white connector block through the frame and also the sensor wires, the connector block for this can be found behind the nearside black tear drop fill panel (green and blue wires IIRC)Now you can undo the bolts holding the casing on.Have an oil pan and cloths under the bike now because you will loose some oil here.Once the bolts are out it's just a matter of sliding the casing off but be careful because the starter gears can come off too no big deal though they just slide back into place.Expect to feel a little resistance here as the magnets try to hold the stator in place.You should be left with the rotor (magnets) and starter gears on the bike.

And the stator and pick up in the casing.

To remove the stator assembly undo the three bolts holing it in and the two bolts holding the sensor and retaining plate in place, lift out the assembly the two grommets and wires as one unit.Be careful with these bolts as they are held in with some kind of thread lock and are really tight. I managed to snap off the ball end of an allen key in one of them which made my job a little harder than necessary.

The rest is common sense from here, clean the casing, remove traces of old gasket from mating faces and put the cover back on with a couple of bolts to keep the dust out of the engine.Now it's up to you what you do but at the time of writing a new stator assembly was £600.I sent mine off to be re-wound at a cost of £55 and a turn around of 3 working days.

I used Robin Williams

Robin Williams 29 Coleman AvenueTeignmouthDevonTQ14 9DU

01626 772791

When you get it back, put the newly wound stator into the casing (don't forget to route the wires correctly) seal the grommets into place with instant gasket and leave in a warm place for 24 hours for the shellac to dry thoroughly (mine was still a bit tacky when I received it).

Replacing everything on the bike is just a reversal of removal. Use a new gasket (£16ish) and when putting the casing on keep a firm grip on it as the magnets will try to pull it out of your hands and you don't want to chip that nice new shellac.When it's all back together check the resistances between the three wires, if it's correct reconnect to the reg/rec and reconnect the pick up then check the oil level, start the bike and run through the check list to make sure everything is ok.If you have made a good job of it reward yourself with some

Did I read (somewhere?) that leaving the stator out for an extended period causes the magents to lose some of thier power? Permanent magnets do this if a 'keeper' is not installed. Just something to be wary of.

Did I read (somewhere?) that leaving the stator out for an extended period causes the magents to lose some of thier power? Permanent magnets do this if a 'keeper' is not installed. Just something to be wary of.

Yeh I know all that but none if it applies to magnets that have just been left.However, I've just spent the last two hours being lectured on the molecular properties of magnets and yes it it is possible (will explain if you want to know) and a keeper will prevent it from happening, that said, I don't see how a keeper could applied to a rotor like this.

LD,I knew someone would call me on this.It is a lot more complicated than this but basically when you magnetise ferrous metals you are aligning all the usually chaotic molecules in the same direction and creating a north and south pole but it is effectively (as an analogy) like an open circuit (electrical) with nothing attracting the north pole to the south pole and over time or with shock, vibration etc the molecular structure can settle back into a chaotic state and lose it's magnetic properties.A keeper completes this circuit and keeps the magnetic field flowing and the molecular structure aligned.If you have ever bought a horseshoe magnet you should have got a keeper with it in the form of a small metal bar across the two poles.Still, I don't see how this knowledge can be applied to the magnets in a rotor.

[quote name='celticbiker' date='Sat 3rd Apr 2010, 11:22 PM' post='157646']
Well after getting home and having a good nights sleep it was time to have a look at the bike and find out why the battery wasn't charging.
If you are new to bike electrics this could seem like a daunting task but in reality there are only a few components in the charging system and one of them can't possibly go wrong.
The whole system consists of (from engine up) a set of rotating magnets, a stator (a set of static coils), 3 wires, a connector, reg/rec, another connector, 2 wires, main fuse and battery.
Fault finding is relatively easy too, I was going to type it out but there is already a fault finding flow chart that can be seen here or if that link is broken it can be downloaded from here free.
The stator readings for the 900 should be 1.8 - 2.8 ohms

Excellent write-up by Celticbiker. I followed it faithfully and to be honest, the hardest thing was disconnecting some of the cables which was only fiddly unless you've got the fingers of a 5 year old. Job done, the offending item is sitting on the table and will be posted off on Tuesday after the holiday. Thanks mate. Much appreciated. I now need to re-read the bit about putting it back together.
Ali

The main lead should be lead in behind the sensor, not direct to the stator - which has resulted in the rotor rubbing through the main connecting wires. Poor work by the garage that fixed it. Not sure if the stator has not been shorted out because of this.

Excellent write-up by Celticbiker. I followed it faithfully and to be honest, the hardest thing was disconnecting some of the cables which was only fiddly unless you've got the fingers of a 5 year old. Job done, the offending item is sitting on the table and will be posted off on Tuesday after the holiday. Thanks mate. Much appreciated. I now need to re-read the bit about putting it back together.Ali[/quote]

Re-fitted the stator today and am happy to report that I am now getting 14.2 volts on the meter. Went for a spin so it looks like I'm riding to work tomorrow. Thanks once again for detailed instructions, Celticbiker. Oh, and I used Robin for the rewind. He turned it round in 2 days. Great service.Ali

Hello,Great tutorial Celticbiker!I live in the South of France and I recently got issues with the charging system. I have been trying to figure out what is wrong by myself but it is not easy...

> "The stator readings for the 900 should be 1.8 - 2.8 ohms">The service manual reads the stator coil resistance should be 0.18 ~ 0.28 ohms at 20C. Did you mistype it or is it a typo in the service manual ?On my bike (TDM900 2003), I measured it on the grey connector (with the 3 white wires coming from the alternator) after having unplugged it from the regulator. I got the same result for all 3 combinations: 1 ohm.Is the grey connector the right place to take the measurements ? Or should I take the measurements right at the stator ?Indeed I am afraid of removing the cover, especially if it is the regulator that is in fault. By the way, do you know if there is a way to test the regulator ?

> "Have an oil pan and cloths under the bike now because you will loose some oil here.">Do you mean there is going to be a few drops or all the engine oil will drain off ?

Hello,Great tutorial Celticbiker!I live in the South of France and I recently got issues with the charging system. I have been trying to figure out what is wrong by myself but it is not easy...

> "The stator readings for the 900 should be 1.8 - 2.8 ohms">The service manual reads the stator coil resistance should be 0.18 ~ 0.28 ohms at 20C. Did you mistype it or is it a typo in the service manual ?On my bike (TDM900 2003), I measured it on the grey connector (with the 3 white wires coming from the alternator) after having unplugged it from the regulator. I got the same result for all 3 combinations: 1 ohm.Is the grey connector the right place to take the measurements ? Or should I take the measurements right at the stator ?Indeed I am afraid of removing the cover, especially if it is the regulator that is in fault. By the way, do you know if there is a way to test the regulator ?

> "Have an oil pan and cloths under the bike now because you will loose some oil here.">Do you mean there is going to be a few drops or all the engine oil will drain off ?

Thanks again for the detailed instructions!Matthieu

Yes you are correct it is an error on my part.I drained my oil before I started this job but there will always be about 0.5L in the bottom of the engine. In theory the tank should not drain because of the check valve but I didn't want to find out.